Virtualized block device backing for virtualization containers

ABSTRACT

Technologies are provided for backing virtualization containers with layered storage volumes stored in remote storage devices. A virtualization container can present a virtual storage volume to a process running in the virtualization container and handle data access requests from the process using a layered storage volume based on one or more read-only snapshots stored in one or more remote storage devices. Changes can be recorded in a read-write layer in one or more of the remote storage devices and associated with the layered storage volume. A new read-only snapshot can be created based on the data in the read-write storage layer and associated with the one or more read-only snapshots on which the layered storage volume is based. A virtualization container can be associated with a new layered storage volume based on the created read-only snapshot and the one or more read-only snapshots on which it is based.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a Divisional application of U.S. patent application Ser. No.15/377,912, filed Dec. 13, 2016, which is hereby incorporated byreference in its entirety.

BACKGROUND

Operating system-level virtualization (sometimes also referred to as“container virtualization”) was developed as an alternative towhole-system virtualization. Unlike a whole-system virtualization, whichcomprises a separate guest operating system running in a virtual machineon top of a host system, operating system-level virtualization usesvirtualization containers running on top of a host system's operatingsystem kernel. Processes running in virtualization containers can beisolated from one another using features of the host operating system,such as multiple user space instances. Since virtualization containersdo not require guest operating systems, they use less storage space andmemory than virtual machines in many cases, and often can be deployedmore quickly than virtual machines.

Storage space requirements for virtualization containers can be furtherreduced in at least some cases by using layered container images. Alayered container image comprises one or more read-only image layers.When data changes are made, instead of modifying the data directly inthe layer where it resides, a new image layer is added and the changesare recorded in the new layer. Virtualization containers can shareaccess to image layers. In some cases, this can reduce deployment timeand storage space requirements since a given image layer may only haveto be copied to a given host computer once. However, these potentialtime and space savings depend largely on the amount of overlap betweencontainer images used by virtualization containers on a given host.Furthermore, each image layer must still be copied to a given hostcomputer at least once.

Therefore, there exists ample opportunity for improvement intechnologies related to data storage and organization for virtualizationcontainers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram showing an example system comprising avirtualization container configured to access a layered virtual volumein a distributed block store.

FIG. 2 is a flowchart of an example method for creating a storage volumefor a virtualization container based on an image manifest.

FIG. 3 is a system diagram showing an example system comprising avirtualization container configured to present a virtual storage volumebacked by a layered remote storage volume.

FIG. 4 is a flowchart of an example method for creating a virtualizationcontainer connected to a remote storage volume.

FIG. 5 is a system diagram showing an example system configured topresent a mounted volume to a virtualization container based on alayered virtual volume in a distributed storage.

FIG. 6 is a system diagram showing an example system comprising multiplevirtualization containers with mounted volumes backed by differentvirtual volumes in a distributed storage.

FIG. 7A is a system diagram showing an example system 700 comprising avirtualization container connected to a virtual volume based on an imagemanifest.

FIG. 7B is another system diagram showing the example system 700comprising a new image manifest based on changes made by thevirtualization container.

FIG. 8 is a flowchart of an example method for creating a remote imageusing layers of snapshots in a remote storage.

FIG. 9 is a system diagram showing an example system configured toservice data access requests from a virtualization container using alayered storage volume stored in a distributed block storage.

FIG. 10 is a system diagram showing an example system configured topresent a mounted volume to an application in a virtualization containerbased on a layered virtual volume in a distributed storage.

FIG. 11 depicts a generalized example of a suitable computingenvironment in which the described innovations may be implemented.

DETAILED DESCRIPTION

Although layered container images may reduce storage and deployment timerequirements for virtualization containers in some cases, such savingsare only applicable to scenarios where multiple virtualizationcontainers on a given host computer require the same (or some of thesame) container image layers. If a given virtualization containerrequires an image layer that is not already present on the hostcomputer, the image layer must be copied to the host computer before aprocess can be launched within the virtualization container.Furthermore, each container image layer must be copied to each hostcomputer at least once. This means that changes to services and/orapplications must still be deployed to each host computer where avirtualization container running a service and/or application isinstantiated. Even with each image layer only being deployed to eachhost computer once, deploying a container image to several differenthost computers can take a significant amount of time and consume asignificant amount of storage space.

At least some of the embodiments of the technologies described hereinsolve these problems by linking virtualization containers to layeredstorage volumes stored in one or more remote storage devices. Forexample, instead of copying a container image to a host computer andthen instantiating a virtualization container based on the containerimage, a virtualization container can be instantiated on the hostcomputer and configured to access a remote layered storage volume.

In one embodiment, a virtualization container is configured to tunneldata access requests from one or more processes running in thevirtualization container to a storage service. The storage service isconfigured to process the data access requests using a layered storagevolume stored in one or more storage devices, wherein the layeredstorage volume is based on one or more read-only data snapshots.

In a different or further embodiment, a storage service is configured tocreate a container image using a layered storage volume associated witha virtualization container. The storage service can identify one or moreread-only snapshots in one or more remote storage devices on which thelayered storage volume is based and generate an image snapshot manifestidentifying the one or more read-only snapshots. The storage service canthen register the image snapshot manifest with an image repository. In afurther embodiment, the storage service can detect data changes recordedin a read-write storage layer associated with the layered storage volumeand create a new read-only snapshot in the remote one or more storagedevices based on the detected changes. In such an embodiment, the newread-only snapshot can be included in the image snapshot manifest.

In a different or further embodiment, a virtualization container on ahost computer can be linked to a new layered storage volume based on animage snapshot manifest. The image snapshot manifest can be retrievedfrom an image repository and analyzed to identify one or more read-onlydata snapshots. The one or more read-only data snapshots can be locatedin a remote storage comprising one or more storage devices. A newlayered storage volume can be created in the remote storage, based onthe one or more read-only snapshots. The new layered storage volume canbe associated with the virtualization container and a process running inthe virtualization container can interact with the linked layeredstorage volume as if it were a physical storage volume mounted directlyto the host computer.

FIG. 1 is a system diagram showing an example system 100 comprising ahost computer 110 comprising one or more virtualization containers(e.g., 114-116) configured to perform data access operations via aremote storage service 120. The remote storage service 120 is configuredto access a layered storage volume 132 in a distributed block storage130. Upon receipt of a data access operation from the virtualizationcontainer 114, the storage service 120 is configured to access dataand/or perform data manipulation on one or more data items stored thelayered storage volume 132.

The layered storage volume 132 is a layered virtual volume that is basedon at least one read-only snapshot 142. The read-only snapshot 142comprises one or more data items (not shown) that cannot be modified bydata operations. In at least one embodiment, layered storage volume 132is based on multiple read-only snapshots 142-144. In such an embodiment,each snapshot represents successive additions, modifications, and/ordeletions of data items stored in a previous read-only snapshot. Thestorage service 120 is configured to process the one or more read-onlysnapshots 142-144 associated with the virtual layered storage volume 132and to present a “flattened” view of the data associated with thelayered storage volume 132 to the virtualization container 114.

The storage service 120 is connected to an image registry 150 comprisingimage manifests 152. An image manifest can comprise a list of one ormore read-only image layers associated with a given image. In at leastone embodiment, an image manifest listing more than one read-only imagelayer also describes a dependency (or lineage) relationship among themore than one read-only image layers. An image (a.k.a. a containerimage) can be presented to a virtualization container (e.g., 114) as asingle, consolidated volume that can be mounted to a filesystem exposedto the virtualization container. Either directly, or via the storageservice 120, the image registry 150 can be inspected to identify one ormore images from which virtual volumes can be created. Once an image hasbeen selected, the storage service 120 can retrieve an image manifest(of the image manifests 152) that is associated with the selected image.For example, an image can be identified by a unique identifier and theimage manifest can be associated with the image identifier in the imageregistry 150. The storage service 120 can inspect the retrieved imagemanifest to identify one or more read-only image layers associated withthe image. In at least one embodiment, the image manifest can containidentifiers of one or more read-only image layers that make up theimage. An identifier for a read-only image layer can comprise a hash ofdata associated with the read-only image layer, although other types ofidentifiers are also possible.

In some scenarios, a requested image manifest may not be found in theimage manifests 152. In such a scenario, the storage service 120 canattempt to locate image layer information for the requested image inanother location, such as a third-party container image repository 160.The third-party container image repository 160 can be a third-partyservice configured to store information about container images. Thethird-party container image repository 160 can be hosted on one or moreservers that is/are accessible by the storage service 120 over anetwork. The information stored about container images in thethird-party container image repository 160 can comprise informationidentifying one or more read-only image layers associated with a givenimage. In a further embodiment, the third-party container imagerepository 160 can store the read-only image layers associated with theimage.

In at least one embodiment, the storage service 120 can inspectinformation about the requested image that is stored in the third-partycontainer image repository 160 to identify one or more read-only imagelayers associated with the requested image. The storage service canconstruct an image manifest for the requested image that comprises alist of the one or more read-only image layers. The storage service 120can then store the created image manifest in the image registry 150 inassociation with the requested image. In a different or furtherembodiment, the third-party container image repository 160 can beconfigured to store image manifests. In such an embodiment, the storageservice 120 can retrieve an image manifest for the requested image fromthe third-party container image repository 160 and store it in the imageregistry 150 in association with the requested image. Although onethird-party container image repository 160 is depicted in FIG. 1, it ispossible for the storage service 120 to access multiple third-partycontainer image repositories. For example, a different read-only imagelayers can be retrieved from multiple different repositories.

The storage service 120 can identify one or more read-only snapshots(e.g., 142) stored in the distributed block storage 130 that areassociated with the identified one or more read-only image layersassociated with the requested image. The storage service 120 can createa new virtual volume (e.g., 132) in the distributed block storage 130and associate the created virtual volume with the one or more identifiedread-only snapshots (e.g., 142). In at least one embodiment, the storageservice 120 can identify a read-only snapshot associated with a givenread-only image layer using image layer-snapshot mappings 122 stored inthe storage service 120. For example, the image layer-snapshot mappings122 can comprise associations between read-only image layer identifiersand storage locations of read-only snapshots (e.g., 142) in thedistributes block storage 130 that contain data for the associatedread-only image layers. In a different or further embodiment, thestorage service 120 can identify read-only snapshots associated with theidentified read-only image layers using a separate image layer-snapshotmapping service 170. In such an embodiment, the storage service 120 cantransmit an identifier of a read-only image layer to theimage-layer-snapshot mapping service 170 and receive a storage locationin the distributed block storage 130 of a read-only snapshot associatedwith the read-only image layer in response.

In some cases, one or more of the identified read-only image layers maynot be associated with read-only snapshots in the distributed blockstorage 130. In at least one embodiment, when an identified read-onlyimage layer is not associated with a read-only snapshot in thedistributed block storage 130, the storage service 120 can attempt tolocate the read-only image layer in a separate storage location, such asthe third-party container image repository 160. If the storage service120 is able to locate the read-only image layer in the third-partycontainer image repository 160, then the storage service 120 canretrieve the data for the read-only image layer from the third-partycontainer image repository 160 and create a new read-only snapshot inthe distributed block storage 130 using the retrieved data. The imagelayer—snapshot mappings 122 (and/or the image-layer—snapshot mappingservice 170) can be updated to include a mapping between the read-onlyimage layer and the created read-only snapshot.

In at least one embodiment, creating a new read-only snapshot in thedistributed block storage 130 using the data for a read-only image layercan comprise writing the data to a layered storage volume in thedistributed block storage 130 and then creating a new read-only snapshotbased on the data written to the layered storage volume. For example,the storage service 120 can create a new layered storage volume in thedistributed block storage 130 and can write the data for the read-onlyimage layer to a read-write storage layer of the layered storage volume.The storage service 120 can then create a read-only snapshot of the datastored in the layered storage volume's read-write storage layer.Optionally, the storage service 120 can create a new read-write storagelayer for the layered storage volume and associate the new read-writestorage layer with the created read-only snapshot.

In a scenario where an image manifest identifies more than one read-onlyimage layer associated with an image, it is possible for one of theread-only image layers to be associated with a read-only snapshot in thedistributed block storage 130 and for another of the read-only imagelayers to not be associated with a read-only snapshot. In such ascenario, the storage service 120 can create a new read-only snapshotfor the read-only image layer that was not already associated with aread-only snapshot and associate the created read-only snapshot with theread-only snapshot that already existed.

For example, the storage service 120 can analyze a given image manifestand determine that the image manifest identifies two read-only imagelayers: a first read-only image layer and a second read-only image layerthat is based on the first read-only image layer. The storage service120 can ascertain that the first read-only image layer is associatedwith the read-only snapshot 144 in the distributed block storage 130,and that the second read-only image layer is not associated with aread-only snapshot in the distributed block storage 130. The storageservice 120 can retrieve data for the second read-only image layer froma remote source (such as the third-party container image repository 160)and create the read-only snapshot 142 in the distributed block storage130 using the data for the second read-only image layer. The storageservice 120 can associate the read-only snapshot 142 with the read-onlysnapshot 144 to indicate that the read-only snapshot 142 is based on theread-only snapshot 144. The storage service can update the imagelayer—snapshot mappings 122 (and/or the image layer—snapshot mappingservice 170) to indicate that the read-only snapshot 142 is associatedwith the second read-only image layer. Subsequently, the storage service120 can create a layered storage volume based on an image that comprisesthe second read-only image layer using, at least in part, the read-onlysnapshot 142.

In a particular embodiment, the first read-only image layer canrepresent an operating system and the second read-only image layer canrepresent one or more applications and/or services installed on top ofthe operating system. In such an embodiment, the layered storage volume132 based on the read-only snapshot 142 (containing the data for the oneor more applications and/or services) and the read-only snapshot 144(containing the data for the operating system) can be presented to thevirtualization container 114 as a “flattened file system containing thedata for the operating system and the one or more applications and/orservices.

In an embodiment where the image manifest lists only one read-only imagelayer, the storage service 120 can identify a read-only snapshot in thedistributed block storage 130 associated with the read-only image layerand associate a new virtual volume with the one read-only snapshotdirectly. In an embodiment where the image manifest lists multipleread-only image layers, the storage service 120 can attempt to identifya dependency (or lineage) relationship among the multiple read-onlyimage layers. This can be done, for example, by analyzing informationabout the dependency (or lineage) relationships recorded in the imagemanifest. Additionally or alternatively, the storage service 120 canidentify read-only snapshots associated with the multiple read-onlyimage layers and the identified read-only snapshots can identify thedependency (or lineage) relationship among themselves. For example, agiven read-only snapshot may indicate another read-only snapshot uponwhich it is based. That another read-only snapshot may, in turn,indicate a third read-only snapshot upon which it is based, and so on.Once the dependency (or lineage) relationship among the multipleread-only snapshots has been ascertained, the storage service 120 canassociate the new virtual volume with a most recent of the read-onlysnapshots.

The virtualization container 114 can be used by the host operatingsystem kernel 112 to execute one or more processes in isolation fromother processes running on the host computer 110. The layered storagevolume 132 in the distributed block storage 130 can be presented to theone or more processes running in the virtualization container 114 as aphysical storage volume (not shown) mounted to a filesystem exposedwithin the virtualization container 114. In at least one embodiment, aprocess running in the virtualization container 114 can access thelayered storage volume 132 as if it were a physical storage volumemounted directly to the host computer 110. When the process running inthe virtualization container 114 attempts to access the mounted storagevolume, the virtualization container 114 can transmit data accessedrequests to the storage service 120, which can access the layeredstorage volume 132.

Optionally, the host computer 110 can comprise additional virtualizationcontainers (e.g., 116) for running additional processes in isolation. Insuch an embodiment, the additional virtualization containers (e.g., 116)can also be configured to access the storage service 120 and to presentdifferent mounted volumes backed by other layered storage volumes (notshown) in the distributed block storage 130. The different virtualvolumes in the distributed block storage, that are associated withdifferent virtualization containers, can be associated with some or allof the same read-only snapshots stored in the distributed block storage.

In any of the examples described herein, a virtualization container canbe a virtual runtime environment that groups and/or isolates one or moreprocesses from other processes running on a host computer. A hostcomputer can instantiate one or more virtualization containersassociated with different processes. Unlike virtual machines,virtualization containers on a host computer share a same kernel of ahost operating system. Technologies for creating virtualizationcontainers are sometimes referred to as “operating systemvirtualization.” Example virtualization technologies that can be used toimplement virtualization containers include DOCKER libcontainer, LXC,OpenVZ, LINUX VServer, BSD Jails, SOLARIS zones, system-nspawn,libvirt-lxc, libvirt-sandbox, qemu/kvm, chroot, etc.

A virtualization container can be associate with resources of a hostcomputer, such as memory, CPUs (or CPU cores), GPU, storage devices,network resources, etc. Constraints can be placed on a virtualizationcontainer's resource utilization. For example, an amount of the hostcomputer's system resources (CPU, memory, network bandwidth,communication ports, storage capacity, etc.) that processes in a givenvirtualization container can use can be limited. In a scenarios wheremore than one virtualization container is instantiated on a given hostcomputer, different system resource constraints can be applied to thedifferent virtualization containers.

In any of the examples described herein, a storage device can be anydevice capable of storing data in one or more physical storage media.For example, a storage device can be a magnetic storage device, such asa hard disk drive. Other examples of storage devices include solid statestorage devices (such as NAND-type flash devices and NOR-type flashdevices), and random access data storage devices (such as DRAM devices).

In some embodiments, a storage device comprises a storage devicecontroller configured to receive data access commands and perform readand write operations on the one or more physical storage media.

In any of the examples described herein, a remote storage device is astorage device that is not directly connected to a host computer onwhich a virtualization container is instantiated. A remote storagevolume is a storage volume (such as a layered storage volume) that isstored on one or more remote storage devices.

In any of the examples described herein, a distributed storage can be astorage system comprising multiple storage devices. In at least someembodiments, data is stored redundantly across multiple storage devicesin a distributed storage. In a scenario where data is storedredundantly, a given piece of data can potentially be retrieved frommore than one storage device. In a different or further embodiment, dataitems stored in a distributed storage can be sharded. When a data itemis sharded, it is divided into multiple pieces and the multiple piecescan be stored on separate storage devices in the distributed storage. Asharded data item can be retrieved by retrieving the shards from themultiple storage devices and assembling them to reform the data item. Inat least one case, shards can be stored redundantly so that less thanall of the storage devices on which shards for a given data item arestored are required to reassemble the data item.

In a different or further embodiment, a distributed storage can be adistributed block storage. In a distributed block storage, a data itemcan be separated into multiple data blocks and the data blocks can bestored across multiple storage devices. A data item can be retrieved byretrieving the data blocks and reforming the data item. In at least somecases, the data blocks for a given data item can be stored redundantlyacross multiple storage devices. In at least some embodiments, datablocks for data items are individually addressable and can be targetedby data access operations using their individual addresses. In a furtherembodiment, data blocks in a distributed block storage can be associatedwith logical addresses (such as logical block addresses (LBAs)) andphysical addresses. In such an embodiment, data blocks can be accessedusing their logical addresses, which are used to locate the physicaladdresses where the blocks are stored. In at least one case, where datablocks are stored redundantly, a logical address for a data block can beassociated with multiple physical addresses representing the multiplelocations where copies of the given data block are stored.

In at least some embodiments, a distributed storage can comprise a cacheconfigured to provide faster access to frequently requested data items.In a distributed storage, read-only data snapshots and/or read-writestorage layers associated with storage volumes can be stored on one ormore storage devices, in whole or in part.

In any of the examples described herein, a host computer can be a serveror other computing device that comprises a processor and is configuredto communicate over a network. The host computer can be connected to oneor more storage devices and can be configured to transmit data accessrequests (such as data read and write operation requests) to the one ormore storage devices and receive responses from the one or more storagedevices. The connection can be an indirect connection, such as aconnection over a network. In scenarios where the host computer isconnected to more than one storage device, the various connections canbe of the same type or different types. In at least some embodiments,the host computer is configured to communicate with the one or morestorage devices through a storage service. A host computer can furthercomprise memory, and/or one or more local storages. In at least oneembodiment, a host computer can be a virtual machine and the systemresources of the host computer (processor, memory, storage capacity,network interface, etc.) can be virtual resources exposed to the hostcomputer (for example by a hypervisor). A host computer can beconfigured to instantiate one or more virtualization containers and torun one or more processes in the one or more virtualization containers.

FIG. 2 is a flowchart of an example method 200 for creating a storagevolume for a virtualization container based on an image manifest. Any ofthe example systems described herein can be used to perform the examplemethod 200. For example, all or part of the example method 200 can beperformed by a storage service such as the storage service 120 depictedin FIG. 1. Alternatively or additionally, all or part of the examplemethod 200 can be performed by a driver or other program on a hostcomputer.

At 202, a command is received to create a storage volume for avirtualization container based on an image manifest. The command cancomprise an identifier for the image manifest, such as a uniqueidentifier associated with the image manifest in an image repository orimage registry. The image manifest can be retrieved from the imagerepository or image registry using the provided identifier. Once theimage manifest has been retrieved, contents of the manifest can beanalyzed to identify one or more read-only image layers that make up acontainer image associated with the image manifest.

At 204, a read-only image layer associated with the image manifest isidentified. In at least one embodiment, the image manifest comprises alist of identifiers for one or more read-only image layers that make upthe associated container image. In such an embodiment, the read-onlyimage layer can be identified by processing the list of read-only imagelayer identifiers. For example, the identified read-only image layer canbe an image layer associated with a first of the identifiers in thelist. In a scenario where the list of read-only image layer identifierscomprises more than one identifier, the identifiers can be organized insuch a way as to reflect a dependency relationship between theassociated read-only image layers. For example, the first identifier inthe list can identify a base read-only image layer, and subsequentidentifiers can identify read-only image layers that representsubsequent changes to, additions to, and/or deletions of data containedin previous layers (including the base layer and/or any interveningread-only image layers). Alternatively, a last identifier in the listcan identify the base read-only image layer and the first identifier inthe list can identify a most-recent set of changes to, additions to,and/or deletions of data contained in previous layers.

At 206, a remote storage device is searched for a snapshot associatedwith the identified read-only image layer. In one embodiment, the remotestorage device stores one or more data files comprising mappings betweenread-only image layer identifiers and read-only snapshots stored in theremote storage device, wherein a mapping between a given read-only imagelayer identifier in a read-only snapshot indicates that the read-onlysnapshot stored on the remote storage device contains data for theread-only image layer. In such an embodiment, the one or more data fileson the remote storage device can be searched for a mapping entry thatcontains an identifier for the identified read-only image layer. In adifferent or further embodiment, mappings between read-only image layeridentifiers and read-only snapshots can be stored in a separatelocation, such as in a storage medium and/or memory of a server runninga storage service.

In at least one embodiment, the remote storage device comprises multiplestorage media organized in a distributed storage, such as a distributedblock storage.

At 208, a check is made to see if the snapshot associated with theidentified read-only image layer was found. If a snapshot associatedwith the read-only image layer was found on the remote storage device,then at 210 a remote storage volume is created based on the snapshot.Creating a remote storage volume can comprise creating a new read-writestorage layer for the remote storage volume on the remote storage deviceand associating the new read-write storage layer with the snapshot. Theassociation can comprise a relationship that indicates that the newread-write storage layer is based on the snapshot associated with theread-only image layer. At 212, the remote storage volume is connected tothe virtualization container. Example technologies for connecting aremote storage volume to a virtualization container are describedherein.

If a snapshot associated with the identified read-only image layer wasnot found, then at 214 a new snapshot is created in the remote storagedevice for the read-only image layer. Creating the new snapshot cancomprise searching one or more third-party image registries and/or imagerepositories for the identified read-only image layer. If the read-onlyimage layer is found in a third-party image registry or imagerepository, then data associated with the read-only image layer can beretrieved from the third-party image registry or image repository. Oncethe data for the read-only image layer is retrieved, a new snapshot canbe created in the remote storage device using the retrieved data.Creating the new snapshot can comprise writing the data for theread-only image layer to one or more storage locations (such as one ormore physical storage media, one or more data blocks on one or morephysical storage media, etc.) in the remote storage device. In adifferent or further embodiment, creating the new snapshot can comprisecreating a new mapping entry associating one or more storage locationswhere the data for the read-only image layer is stored in the remotestorage device with the identifier for the read-only image layer. In adifferent or further embodiment, one or more storage locations wheredata for the read-only image layer is stored in the remote storagedevice can be marked as read-only to prevent the data from beingmodified by subsequent data operations.

At 216, the virtualization container is connected to a remote storagevolume that is based on the new snapshot. In at least one embodiment,the virtualization container is created as part of the snapshot creationprocess. For example, a new remote storage volume can be created that isnot based on any pre-existing snapshots. Such a remote storage volumecan comprise a read-write storage layer on the remote storage devicethat is not based on a snapshot. Once data for the read-only image layerhas been retrieved, the data can be written to the read-write storagelayer of the remote storage volume. The new snapshot can be created, forexample, by marking the read-write storage layer (or portions of theread-write storage layer that contain data for the read-only imagelayer) as read-only. Alternatively or additionally, locations in theread-write storage layer storing data for the read-only image layer canbe associated with the identifier for the read-only image layer in amapping entry. Optionally, a new read-write storage layer can be createdfor the remote storage volume, wherein the new read-write storage layeris based on the new snapshot. The remote storage volume can then beconnected to the virtualization container.

In a scenario where the image manifest identifies more than oneread-only image layer, snapshots can be located and/or created in theremote storage device for each of the read-only image layers. Forexample, a most-recent read-only image layer that is associated with asnapshot in the remote storage device can be identified. This can bedone by attempting to identify snapshots for each of the read-only imagelayers, beginning with the oldest layer (e.g., the base layer), andstopping when a snapshot for a given read-only image layer is not found.Once the most recent read-only image layer that is associated with asnapshot has been identified, a remote storage volume can be createdbased on that snapshot. New snapshots can then be created in the remotestorage device for read-only image layers for which snapshots aremissing. This can be done, for example, by writing data for a read-onlyimage layer to a read-write storage layer of the remote storage volumeand then creating a snapshot of the remote storage volume. This processcan be repeated for any remaining read-only image layers identified bythe image manifest. Once snapshots have been identified or created foreach of the read-only image layers identified in the image manifest, theremote storage volume can be connected to the virtualization container.

In at least one embodiment, data for read-only image layers can beretrieved from multiple different image registries and/or imagerepositories. For example, data for a first read-only image layer can beretrieved from a first image registry and/or image repository and usedto create a first snapshot. Then data for a second read-only image layercan be retrieved from a second, different image registry and/or imagerepository and can be used to create a second snapshot that is based onthe first snapshot.

At least one embodiment of the technologies described herein comprises amethod for creating a new image based on a remote storage volumeconnected to a virtualization container. Such a method can be performedusing any of the example systems described herein.

In an example method for creating a new image based on a remote storagevolume, a command can be received to create a new image for avirtualization container. The command can be received from thevirtualization container or a process running inside the virtualizationcontainer. Additionally or alternatively, the command can be receivedfrom a separate service configured to monitor and/or perform maintenanceoperations on the virtualization container. A snapshot can be created ofa remote storage volume connected to the virtualization container. Theremote storage volume can be a layered storage volume stored on one ormore remote storage devices connected to a host computer where thevirtualization container is instantiated. The remote storage volume canbe connected to the host computer via one or more network connections.The remote storage volume can be a virtual volume in a distributedstorage, such as a distributed block storage.

Creating a snapshot of the remote storage volume can comprise creating aread-only copy of data stored in the remote storage volume. In anembodiment where the remote storage volume is a layered storage volume,creating the snapshot can comprise identifying differences between thelayered storage volume and another snapshot on which the layered storagevolume is based. Once such differences are identified, the differencescan be stored in the created snapshot. The created snapshot can then beassociated with the another snapshot, such as with a relationship thatindicates that the created snapshot is based on the another snapshot.

In at least one embodiment, the remote storage volume comprises areference to a read-only snapshot and data read requests directed toremote storage volume are serviced by retrieving data from the read-onlysnapshot. In such an embodiment, when a data write request is received,such as from a process executing in the virtualization container, aread-write storage layer can be created in the remote storage volume anddata contained in the data write request can be written to theread-write storage layer. In such an embodiment, determining differencesbetween the remote storage volume and the snapshot on which the remotestorage volume is based can comprise identifying the date written to theread-write storage layer and storing a read-only copy of the identifieddata in the created snapshot.

The created snapshot can be stored in a remote storage device. Theremote storage device can be the same remote storage device on which theremote storage volume is stored. In an embodiment where the remotestorage volume is a layered storage volume based on one or more otherread-only snapshots, the created snapshot can be stored on a samestorage device as the other one or more read-only snapshots.Additionally or alternatively, the created snapshot can comprisemultiple data blocks that are stored on multiple different storagedevices in a distributed block storage.

The created snapshot can be registered as a new image with an imagerepository.

Registering the created snapshot can comprise generating an imagemanifest that identifies the created snapshot as a basis for a newcontainer image and transmitting the generated image manifest to theimage repository. In an embodiment where the remote storage volume is alayered storage volume based on one or more other read-only snapshots,the generated image manifest can identify the created snapshot, the oneor more other snapshots, and a relationship between the created snapshotand the one or more other snapshots. For example, the image manifest canindicate that the created snapshot is based on one of the one or moreother snapshots and comprises changes and/or additions to data stored inthe one of the one or more other snapshots. The image manifest can alsoidentify similar relationships between the one or more other snapshots.By analyzing such relationships, a service wishing to create a newvolume using the image manifest can create a dependency (or lineage)graph of the related snapshots and associate the new volume with a mostrecent of the snapshots.

FIG. 3 is a system diagram showing an example system 300 comprising avirtualization container 320 configured to present a virtual storagevolume 324 to a process 322, wherein the virtual storage volume 324 isbacked by a layered remote storage volume 342 in a storage device 340.The virtualization container 320 is configured to execute the process322 in isolation from other processes (not shown) executing on the hostcomputer 310 and to present the virtual storage volume 324 to theprocess 322 as a physical storage volume connected to the virtualizationcontainer 320. Presenting the virtual storage volume 324 to the process322 as a physical storage volume can comprise reporting the virtualstorage volume 324 to the process 322 as a mounted storage volume and/orallowing the process 322 to detect the virtual storage volume 324 as amounted storage volume, and allowing the process 322 to access thevirtual storage volume as if it were a mounted storage volume. Thevirtualization container 320 is configured to receive data accessrequests targeting the virtual storage volume 324 from the process 322and to transmit data access requests to a storage service 330 that isseparate from the host computer 310, in order to access data stored inthe remote storage volume 342.

The storage service 330 is configured to receive the data accessrequests from the virtualization container 320 and to access the remotestorage volume 342 on the storage device 340 over a network. The remotestorage volume 342 is a layered storage volume associated with one ormore read-only data snapshots, such as read-only snapshot 344. Thestorage service 330 is further configured to process the data accessrequests using the read-only data snapshot 344. Although only a singleread-only snapshot 344 is depicted, the remote storage volume 342 can bebased on more than one read-only snapshot.

In a particular example, the process 322 can request data from thevirtual storage volume 324. The virtualization container 320 cantransmit one or more data read requests to the storage service 330 toretrieve the requested data from the remote storage volume 342. Thestorage service 330 can analyze the read-only snapshot 344 associatedwith the remote storage volume 342 and determine that at least part ofthe requested data is stored in the read-only snapshot 344. The storageservice 330 can then retrieve the at least part of the requested datafrom the read-only snapshot 344 and transmit it back to thevirtualization container 320. Upon receipt of the at least part of therequested data, the virtualization container 320 can provide the atleast part of the requested data to the process 322 as if it wasretrieved from the virtual storage volume 324.

In another particular example, the process 322 can request thatadditional data be written to the virtual storage volume 324. Inresponse, the virtualization container 320 can transmit one or more datawrite requests to the storage service 330. The storage service 330 cancreate a read-write storage layer associated with the remote storagevolume 342. The storage service 330 can store the read-write storagelayer in the storage device 340 or in another storage device (notshown). In at least one embodiment, the storage device 340 is part of adistributed storage comprising multiple storage devices. In such anembodiment, the storage service 330 can store different parts of theread-write storage layer in multiple storage devices in the distributedstorage. The storage service 330 can then write data contained in theone or more data write requests to the read-write storage layer.

Optionally, after writing the data to the read-write storage layerassociated with the remote storage volume 342, the storage service 330can transmit a write confirmation message to the virtualizationcontainer 320. The confirmation message can comprise one or more logicaladdresses associated with the read-write storage layer at which the datawas written. The virtualization container 320 can present the one ormore logical addresses to the process 322 as logical addresses withinthe virtual storage volume 324 at which the data was written.

In another particular example, the process 322 can request that datastored in the virtual storage volume 324 be modified and/or deleted. Thevirtualization container 320 can transmit one or more data writerequests to the storage service 332 modify and/or delete the identifieddata.

In the case of the data modification, the storage service 330 can copythe identified data from the read-only snapshot 344 into a read-writestorage layer associated with the remote storage volume 342 and thenmodify the copy of the data. For example, the storage service 330 canidentify a data block in the read-only snapshot 344 that is a target ofa data write request and copy the contents of the targeted data blockinto a new data block in the read-write storage layer associated withthe remote storage volume 342. The storage service 330 can then make anychanges requested by the data write request to the contents of the datablock in the read-write storage layer. The data in the read-writestorage layer can be associated with a logical address that waspreviously associated with the unmodified data in the read-onlysnapshot. Subsequent data access requests targeting the logical addresscan be handled by the storage service 330 using the modified copy of thedata in the read-write storage layer instead of the unmodified versionof the data in the read-only snapshot 344.

In the case of a deletion, the storage service 330 can identify data inthe read-only snapshot 344 that is a target of the deletion and identifyone or more logical addresses associated with the targeted data in theread-only snapshot 344. The storage service 330 can then create adeletion flag (also referred to as a “white-out mark”) in a read-writestorage layer associated with a remote storage volume 342 and associatethe deletion flag with the one or more identified logical addresses.Subsequent data access requests targeting the one or more logicaladdresses can be handled by the storage service 330 by locating thedeletion flag in the read-write storage layer and returning a message tothe virtualization container 320 indicating that the requested data hasbeen deleted.

Data written to a read-write storage layer of the remote storage volume342 (and any deletion flags) can be used by the storage service 330 tocreate a new snapshot. The new snapshot (and its dependency upon theread-only snapshot 344) can be registered as a new container image fromwhich the virtualization container 320 (or a different virtualizationcontainer) can create a new virtual storage volume.

FIG. 4 is a flowchart of an example method 400 for creating avirtualization container connected to a remote storage volume. Any ofthe example systems described herein can be used to perform examplemethod 400. At 402, a new virtualization container is created on a hostcomputer. Creating the new virtualization container can compriseinstantiating the virtualization container and identifying a containerimage that should be used as the basis for a new storage volume attachedto the virtualization container. At 404, a location of the containerimage is requested from an image repository. The image repository can bean image repository server, an image repository service running on aserver, or the like. It image repository can be configured to receiverequests for container images and transmit locations of snapshotsforming the basis of the requested container images in response.

At 406, a location of a snapshot on a remote storage device is receivedfrom the image repository. In at least one embodiment, an image snapshotmanifest associated with the requested container image is received fromthe image repository. The image snapshot manifest can identify one ormore snapshots associated with the image container and locations of theone or more snapshots on remote storage devices. In different or furtherembodiment, a location or locations of one or more data blocksassociated with one or more read-only snapshots in a distributed blockstorage can be received.

At 408, a remote storage volume based on the one or more snapshotsassociated with the image container is created. In at least oneembodiment, the remote storage volume comprises a read-write storagespace associated with the one or more snapshots. The remote storagevolume can be associated with an identifier that can be used to uniquelyidentify the remote storage volume for subsequent data access requests.At 410, the remote storage volume is connected to the virtualizationcontainer. The connection can comprise transmitting the identifier forthe remote storage volume to the virtualization container and retainingthe identifier by the virtualization container for use in subsequentdata access requests. In at least one embodiment, the remote storagevolume can be presented to one or more processes executing in thevirtualization container as a mounted storage volume. Data accessoperations targeting the mounted storage volume can then be tunneled bythe virtualization container to the remote storage volume.

In a different or further embodiment, data access requests for theremote storage volume comprise the remote storage volume's identifierand are transmitted by the virtualization container to a storageservice. The storage service can use the identifier of the remotestorage volume to identify the one or more snapshots (and optionally aread-write storage space) associated with the remote storage volume inthe remote storage device. Using techniques described herein, thestorage service can perform the requested data access operations usingthe identified one or more snapshots (and optionally the identifiedread-write storage space).

FIG. 5 is a system diagram showing an example system 500 configured topresent a mounted volume 512 to one or more processes (not shown) in avirtualization container 510, wherein the mounted volume 512 is based ona layered virtual volume 532 in a distributed storage 530. Thevirtualization container 510 comprises a storage driver 514 configuredto communicate with a storage service 522 to access the virtual volume532 in the distributed storage 530, and to present the representation ofthe mounted volume 512 within the virtualization container 510. Thestorage driver 514 can be a driver associated with an operating systemof a host computer (not shown) that instantiated the virtualizationcontainer 510. In a different or further embodiment, the storage driver514 can be a special-purpose driver used to allow a process running inthe virtualization container 510 to interact with a layered storagevolume. For example, from the perspective of a process executing in thevirtualization container 510, the mounted volume 512 represented by thestorage driver 514 can appear to be a physical volume connected to thehost computer. In such an embodiment, the storage driver 514 can maskthe fact that the process running in the virtualization container 510 isinteracting with the layered virtual volume 532 in the distributedstorage 530.

The distributed storage 530 comprises multiple storage devices. Thestorage service 520 is configured to store data across the multiplestorage devices in the distributed storage 530 and to present a unifiedview of the data stored in the distributed storage 530 to the storagedriver 514. For example, the storage service 520 can present a unifiedview of the storage capacity of the multiple storage devices in thedistributed storage 530. From the perspective of the storage driver 514,the distributed storage 530 can appear to be a single filesystem orstorage space. When the storage service 520 writes data to thedistributed storage 530, the storage service can write different chunksof the data (such as data blocks) to different storage devices in thedistributed storage 530. When the storage service 520 processes arequest for data stored in the distributed storage 530, the storageservice 520 can locate the chunks of the requested data stored on themultiple storage devices, retrieve the chunks from the storage devices,and reassembled the requested data before transmitting the requesteddata back to the requester.

The storage service 520 is further configured to process data accessrequests received from the storage driver 514 using the virtual volume532 in the distributed storage 530. The virtual volume 532 is associatedwith a read-only snapshot 542. When a data access request is receivedfrom the storage driver 514, the storage service 520 can identify thevirtual volume 532 associated with the storage driver 514 and processthe data access request using the read-only snapshot 542 associated withthe virtual volume 532. In at least one embodiment, the virtual volume532 is associated with multiple read-only snapshots 542-544. In such anembodiment, the read-only snapshots 542-544 constitute multiple layersof data in which each successive snapshot stores additions,modifications, and/or deletions to data stored in the previous snapshot.In such an embodiment, the storage service 520 is configured to processa data access request received from the storage driver 514 byidentifying the most recent snapshot in which the requested data stored.For example, the data access request can comprise a logical addressassociated with requested data. The storage service 520 can identify amost recent snapshot associated with the virtual volume 532 thatcontains one or more data locations associated with the logical address.The storage service 520 can be configured to do this, for example, bystarting with the read-only snapshot 542, upon which the virtual volume532 is directly based, and moving down through the layers of read-onlysnapshots until one or more data locations associated with the logicaladdress is identified. In a different or further embodiment, the storageservice 520 can comprise metadata about the read-only snapshots 542-544associated with the virtual volume 532. The metadata can compriseassociations between logical data addresses and read-only snapshots. Insuch an embodiment, the storage service can inspect the metadata toidentify a read-only snapshot associated with the logical addresswithout inspecting the read-only snapshots in the distributed storage530 directly.

The storage driver 514 can allow a process executing in thevirtualization container 510 to interact with the mounted volume 512 asif it were a flat filesystem or storage space connected directly to thehost computer containing the virtualization container 510, when in factthe storage driver 514 tunnels all data access requests from the processto the storage service 520 which then processes the data access requestsusing the virtual volume 532 in the distributed storage 530.

FIG. 6 is a system diagram showing an example system 600 comprisingmultiple virtualization containers 610-620 with mounted volumes 612-622backed by different virtual volumes 642-644 in a distributed storage640. The virtualization containers 610-620 can be instantiated ondifferent host computers. For example, the virtualization container 610can be instantiated on a first host computer and the virtualizationcontainer 620 can be instantiated on a second host computer.Additionally or alternatively, multiple of the virtualization containers610-620 can be instantiated on one host computer.

The virtualization container 610 comprises a storage driver 614 thatrepresents a mounted volume 612 to one or more processes (not shown)executing in the virtualization container 610 that is backed by thevirtual volume 642 in the distributed storage 640. The virtualizationcontainer 620 comprises a storage driver 624 that represents a mountedvolume 622 to a second one or more processes (not shown) executing inthe virtualization container 620 that is backed by the virtual volume644.

A storage service 630 is configured to receive data access requests fromthe storage drivers 614-624 and to process the data access requestsusing virtual volumes 642-644 in the distributed storage 640. Thestorage driver 630 can determine which virtual volume of the virtualvolumes 642-644 should be used to process a given data access requestreceived from a storage driver (e.g. 614 are 624). For example, a dataaccess request can comprise a virtual volume identifier associated witha virtual volume of the virtual volumes 642-644. The storage service canidentify the virtual volume using the identifier accompanying the dataaccess request and then use the identified virtual volume to process thedata access request.

The virtual volumes 642-644 are layered virtual volumes associated withone or more read-only snapshots (e.g., 652) stored in the distributedstorage 640. Since the virtual volumes 642-644 depend on a same one ormore read-only snapshots 652-654, the mounted volumes 612-622represented by the storage driver 614-624 can represent a same initialdata state to processes executing in the separate virtualizationcontainer 610-620. However, additions, modifications, and/or deletionsfor the different virtual volumes 642-644 will be recorded separately inthe distributed storage 640 by the storage service 630. Thus, asprocesses in the different virtualization containers 610-620 requestalterations or additions, the data states of their respective virtualvolumes 642-644 can begin to diverge.

In at least one embodiment, the storage service 630 can recordadditions, modifications and/or deletions for a given virtual volume, ofthe virtual volumes 642-644, by creating a separate read-write storagelayer for the given virtual volume in the distributed storage 640. In aparticular example, the storage service 630 receives a data accessrequest from the storage driver 614 to add data to the virtual volume642. Responsive to receiving the data access request, the storageservice 630 can identify the virtual volume 642 associated with thevirtualization container 610 and attempt to locate a read-write storagelayer for the virtual volume 642 in the distributed storage 640. If thestorage service 630 cannot locate a read-write storage layer for thevirtual volume 642, the storage service 630 can create a new read-writestorage layer in the distributed storage 640 and associate it with thevirtual volume 642. The storage service 630 can then write datacontained in the request to add data to the read-write storage layerassociated with the virtual volume 642. A subsequent data access requestto read the data added by the add data request can be processed by thestorage service 630 by retrieving the added data from the read-writestorage layer associated with the virtual volume 642. However, asubsequent data access request to read data that was not added by thedata had request can be processed by the storage service 630 byretrieving the data from the one or more read-only snapshots 652-654.

In another particular example, the storage service 630 can receive adata access request from the storage driver 624 to modify data. Thestorage service 630 can identify the virtual volume 644 associated withthe virtual container 620 and determine whether or not a read-writestorage layer stored in the distributed storage 640 is associated withthe virtual volume 644. If a read-write storage layer is not alreadyassociated with the virtual volume 644, the storage service 630 cancreate a new read-write storage layer in the distributed storage 640 andassociate it with the virtual volume 644. The storage service 630 canidentify one or more data storage locations in the one or more read-onlysnapshots 652-654 associated with the virtual volume 644 that containthe data to be modified. The storage service 630 can then copy the datato be modified from the one or more read-only snapshots 652-654 into theread-write storage layer associated with the virtual volume 644. Thestorage service 630 can then modify the data according to the dataaccess request. A subsequent data access request for the modified datacan be processed by the storage service 630 by retrieving the modifieddata from the read-write storage layer associated with the virtualvolume 644. However, a subsequent data access request for the same datalocations received from the storage driver 614 will be processed by thestorage service 630 using the virtual volume 642, with which theprevious data modification request was not processed. Thus, thesubsequent data access request from the storage driver 614 will beprocessed by the storage service 630 by retrieving the unmodified datafrom the one or more locations in the one or more read-only snapshots652-654.

Although the virtual volumes 642-644 are depicted as being based on thesame one or more read-only snapshots 652-654, it is also possible forvirtual volumes to be based on some, but not all, of the same read-onlysnapshots. For example, a different virtual volume (not shown) may bebased on the read-only snapshot 654 but not the read-only snapshot 652.Additionally or alternatively, the different virtual volume may be basedon another read-only snapshot (not shown) on which the virtual volumes642-644 are not based.

FIG. 7A is a system diagram showing an example system 700 comprising avirtualization container 710 connected to a virtual volume 772 in adistributed storage 750 based on an image manifest 732. The imagemanifest 732 comprises a single entry 742 indicating that the image Aassociated with the manifest 732 is based on a single read-only snapshot762 stored in the distributed storage 750. The virtualization container710 is connected to the storage service 720 and is configured to usestorage service for creating and accessing virtual volumes in thedistributed storage 750. For example, the virtualization container 710can transmit a request to the storage service 720 to create a newvirtual volume for the virtualization container 710 based on the imageA. The storage service 720 is configured to retrieve the manifest 732for the image A from an image registry 730 and to analyze the manifest732 to the snapshot 762 in the distributed storage 750 associated withthe image A. The storage service 720 is configured to create a newread-write layer 752 in the distributed store 750 that is based on theread-only snapshot 762 and to associate the read-write layer 752 with anew the virtual volume 772.

The virtualization container 710 can request data from the storageservice 720. Upon receipt of such a request, the storage service 720 canidentify the virtual volume 772 associated with the virtualizationcontainer 710 and process the request using data stored in the read-onlysnapshot 762 associated and/or the read-write layer 752.

The virtualization container 710 can transmit requests to change data(e.g., to add, modify, and/or delete data) to the storage service 720.The storage service 720 can process the requests to change data usingthe read-write layer 752. The storage service 720 can process a requestto add new data by writing the new data to the read-write layer 752 inthe distributed storage 750. The storage service 720 can process arequest to modify data by copying the data to be modified from theread-only snapshot 762 into the read-write layer 752 and then modifyingthe copy in the read-write layer 752. The storage service 720 canprocess a request to delete data by identifying one or more locations inthe read-only snapshot 762 where the data to be deleted to stored and tomark those locations in the read-write layer 752 as deleted.

Once a virtualization container 710 has changed data via one or moredata requests, a new image can be created based on the changes.

FIG. 7B is another system diagram showing the example system 700comprising a new image manifest 734 based on changes made by thevirtualization container 710. The virtualization container 710 cantransmit a request to the storage service 720 to create a new virtualvolume 774 based on changes in the virtual volume 772 currentlyassociated with the virtualization container 710. Upon receipt of therequest to create a new volume 774, the storage service 720 can create anew snapshot 764 of the changes stored in the read-write layer 752. Forexample, storage service 720 can make a read-only copy of data stored inthe read-write layer 752 and store the read-only copy in the distributedstorage 750 as the read-only snapshot 764. In another example, storageservice 720 can convert the read-write layer 752 to the read-onlysnapshot 764 by marking it as read-only and preventing additional datachanges from being applied to it. The storage service 720 can generate anew manifest 734 comprising a list of snapshots 744-742 indicating thata new image B is based on the read-only snapshot 764, which in turn isbased on the read-only snapshot 762. The storage service 720 canassociate the virtualization container 710 with a new virtual volume 774based on the new image B by creating a new read-write layer 754 in thedistributed storage 750 that is based on the read-only snapshot 764.

The image registry 730 can be configured to receive the new imagemanifest 734 from the storage service 720 and to store the manifest 734in association with an identifier (e.g., “Image B”) for the new image.The virtualization container 710 (or another virtualization container)can then request the creation of a new virtual volume (e.g., 774), atleast in part, by providing the identifier for the new image to thestorage service 720.

The virtualization container 710 can transmit a request to the storageservice 720 to access data in the new virtual volume 774. The storageservice 720 can process the request by searching the read-only snapshot764 and/or the read-only snapshot 762 for the requested data.Additionally or alternatively, the virtualization container 710 canrequest subsequent changes to the data in the new virtual volume 774.The storage service 720 can process the subsequent changes using the newread-write layer 754.

Optionally, the virtualization container 710 can comprise an imagecreation script 712 that can be used by the virtualization container 710to perform one or more data change operations in order to generate oneor more new read-only snapshots in the distributed storage 750 and tocreate a new image based on the generated snapshots.

FIG. 8 is a flowchart of an example method 800 for creating a remotecontainer image using layers of snapshots in a remote storage. At 802,an image creation script is retrieved. The image creation scriptcomprises a series of commands that, when executed, will generatechanges to data stored in a target storage volume. The image creationscript can be executed by a process running inside a virtualizationcontainer. In one embodiment, the image creation script can be retrievedby the process running inside the virtualization container and thenexecuted by that process. Alternatively or additionally, the path to theimage creation script can be passed to a container management processthat then creates the virtualization container, launches the processwithin the virtualization container, and instructs the launched processto execute the image creation script. The image creation script can be afile stored in a filed system, a data stream, or the like. Separatecommands within the image creation script can be separated by one ormore delimiters (such as line breaks) and the executing process candetect the end of one command and the beginning of another command bydetecting the one or more delimiters.

At 804, a check is made to see if the end of the image creation scripthas been reached. If the end of the image creation script has not beenreached, then at 806 the next command in the image creation script isprocessed using a storage volume linked to the virtualization container.The linked storage volume can be a remote storage volume that isaccessed by the virtualization container over a network. In at least oneembodiment, the virtualization container accesses the linked storagevolume by transmitting one or more data access requests to a storageservice. The storage service, upon receipt of a data access request fromthe virtualization container, can process the data access request byaccessing data in the remote storage volume.

The remote storage volume can be a layered storage volume based on oneor more read-only snapshots. The remote storage volume can be stored inone or more storage devices. In at least one embodiment, the remotestorage volume comprises data stored across multiple storage devicesorganized in a distributed storage. In such an embodiment, a storageservice can be configured to access the data of the remote storagevolume stored across the multiple storage devices and present a unifiedrepresentation of the remote storage volume to the virtualizationcontainer.

The process running in the virtualization container can process thecurrent command in the image creation script. The command can compriseone or more computational operations and/or one or more data accessrequests targeting the linked storage volume. Example commands caninclude commands to format a filesystem in the linked storage volume;commands to create, modify, and/or delete files and/or folders stored inthe linked storage volume; commands to download and install newapplications and/or program modules in the linked storage volume; etc.

As part of processing the current command, one or more data accessoperations are performed on the linked storage volume. Operations thatadd, modify, and/or delete data in the linked storage volume can beperformed by adding and/or modifying data in a read-write storage layerassociated with the linked storage volume.

At 808, a new snapshot is created from the linked storage volume.Creating the new snapshot can comprise making a read-only copy of datastored in a read-write storage layer associated with the linked storagevolume. Creating the new snapshot can comprise storing the read-onlycopy in one or more storage devices. Alternatively or additionally,creating the new snapshot can comprise marking the existing read-writestorage layer as read-only and preventing additional additions and/ormodifications from being made to the data stored within it. If thelinked volume was based on another snapshot, then an association betweenthe new snapshot and the another snapshot, indicating that the newsnapshot is based on the another snapshot, can also be recorded.

A new read-write storage layer can then be associated with the linkedvolume, which is based on the newly created snapshot. Control can thenreturn to step 804 to determine if any additional commands remain in theimage creation script.

Optionally, instead of associating a new read-write storage layer withthe existing linked volume, at 810, a new storage volume can be createdbased on the new snapshot. Creating the new storage volume can comprisecreating a new read-write storage layer in one or more storage devicesand creating an association between the new read-write storage layer andthe new snapshot, indicating that the new storage volume is based on thenew snapshot. At 812, the new storage volume can be linked to thevirtualization container. Linking the new storage volume to thevirtualization container can comprise removing the link between theprevious storage volume and the virtualization container, and creating anew association between the new storage volume and the virtualizationcontainer. In at least one embodiment, the previous storage volume canbe deleted (or marked as deleted) after the link between it and thevirtualization container has been removed. After the new volume islinked to the virtualization container, control returns to step 804 todetermine if the end of the image creation script has now been reached.

If the script contains more commands to be processed, steps 806-808 (oroptionally steps 806-812) are repeated for each remaining command. Thus,a new snapshot can be created for each command in the image creationscript.

Once the end of the image creation script has been reached, at 814 animage manifest is generated based on the linked storage volume.Generating the image manifest can comprise identifying the snapshots onwhich the linked storage volume is based. This can comprise identifyingthe snapshots that were created by processing the commands in the imagecreation script. If the storage volume that was initially linked to thevirtualization container was based on one or more pre-existingsnapshots, then the pre-existing snapshots can be identified as well.The image manifest can comprise a list of the identified snapshots. Inat least one embodiment, the image manifest further comprises a recordof the dependent (or lineage) relationships between the snapshots. In adifferent or further embodiment, the image manifest can provide a filelocation for each snapshot in one or more remote storage devices. Inthis way, the snapshots stored in one or more remote storage volumes canform the basis of a remote container image.

At 816, the image manifest is registered with an image repository. Theregistering can comprise transmitting the image manifest to an imagerepository service running a separate server. A virtualization containercan request that a virtual volume based on the registered image manifestbe mounted to it. A storage service can retrieve the image manifest fromthe image repository service, create a new storage volume based on theone or more snapshots identified by the image manifest, and link thecreated storage volume to the virtualization container.

FIG. 9 is a system diagram showing an example system 900 configured toservice data access requests from a virtualization container 910 using alayered storage volume stored in a distributed block storage. Thedistributed block storage in the example system 900 comprises multiplestorage devices 920-930 configured to store multiple blocks of data(e.g., 960.1-980.2).

In at least one embodiment, the multiple storage devices 920-930 can belogical storage devices comprising multiple storage media. In such anembodiment, data blocks written to a storage device, of the storagedevices 920-930, can be written to separate storage media of the storagedevice. In a different or further embodiment, a data block written to astorage device can be stored redundantly on multiple storage media ofthe storage device. In a particular embodiment, a logical storage devicecan comprise a storage controller connected to multiple physical storagemedia, wherein the storage controller is configured to receive datablocks and write the received data blocks to the multiple connectedphysical storage media. Examples of logical storage devices in Just aBunch of Disks (JBOD) enclosures, Redundant Array of Independent Disks(RAID) enclosures, etc.

The virtualization container 910 is configured to transmit multiple dataaccess requests (e.g., 942-948) to a storage service 990. The exampledata access requests 942-948 are presented for illustration purposes.Other data access requests are also possible. Although the example dataaccess requests 942-948 are depicted as comprising a single datatransmission from the virtualization container 910 to the storageservice 990, data access requests can be transmitted in separatetransmissions as well.

The storage service 990 is configured to receive the data accessrequests from the virtualization container 910 and to process the dataaccess requests using one or more remote storage volumes stored in thedistributed block storage devices 920-930. The storage service 990 cancomprise metadata about one or more storage volumes and/or read-onlydata snapshots stored in the distributed block storage devices 920-930.For example, in FIG. 9 the storage service 990 is depicted as comprisingmetadata 996 for a storage volume 1 that is based on two snapshotsstored in the distributed block storage devices 920-930. The storageservice 990 is also depicted as comprising metadata 992 for a snapshot 1and metadata 994 for a snapshot 2, on which the storage volume 1 isbased. The storage service 990 can use the storage volume metadata 996to identify the read-only data snapshots stored in the distributed blockstorage devices 920-920, on which the storage volume 1 is based. Thestorage service 990 can use the snapshot metadata to identify storagelocations for data blocks in the distributed block storage devices920-930 associated with a snapshot. For example, using the metadata 992for the read-only data snapshot 1, the storage service 990 can determinethat the data blocks 960.1-960.5 in the storage location 962 on thestorage device 920 are associated with the read-only data snapshot 1.Additionally or alternatively, the storage service 990 can use themetadata 992 to determine that the data blocks 960.6-960.0 in thestorage location 964 on the storage device 930 are associated with thesnapshot 1.

The storage service 990 can use the metadata 994 to determine that thedata blocks 970.1-970.9 in the storage location 972 on the storagedevice 920 are associated with the read-only data snapshot 2.Additionally or alternatively, the storage service 990 can use themetadata 994 to determine that the data blocks 970.A-970.E in thestorage location 974 on the storage device 930 are associated with theread-only data snapshot 2.

The storage service 990 can analyze the data access request 942 todetermine that the data access request 942 is a request to add a newdata block to the storage volume 1. The storage service 990 can analyzethe metadata 996 for the storage volume 1 to attempt to locate aread-write storage layer associated with the storage volume 1. Using themetadata 996, storage service 990 can determine that the storage volume1 is associated with a read-write storage layer comprising a storagelocation 982 on the storage device 920, and a storage location 984 onthe storage device 930. The storage service 990 can then select one ofthe identified storage locations and write the new data block to theselected storage location. For example, FIG. 9 depicts the storageservice 990 as transmitting the new block request 998.2 to the storagedevice 920 to write the new data block 980.1 to the storage location982.

The storage service 990 can analyze the data access request 944 todetermine that the data access request 944 is a request to update a datablock stored in the storage volume 1. The storage service 990 caninspect the metadata 994 and/or 992 to identify a read-only datasnapshot associated with the storage volume 1 that contains the datablock to be updated. For example, the storage volume 1 can be baseddirectly on the read-only data snapshot 2, which in turn can be based onthe read-only data snapshot 1. To identify a most recent version of thedata block to be updated, the storage service 990 can begin byinspecting the metadata 994 associated with the read-only data snapshot2, on which the storage volume 1 is directly based, to attempt toidentify a pointer to a storage location associated with the read-onlydata snapshot 2 that is associated with an address (such as a logicalblock address) of the data block to be updated. If the storage service990 does not find such a pointer in the metadata 994 for the read-onlydata snapshot 2, the storage service 990 can then inspect the metadata992 for the read-only data snapshot 1 to attempt to locate a pointerassociated with the address of the data block to be updated. Forexample, the storage service 990 can identify a pointer to the datablock 970.B in the storage location 974 on the storage device 930 byinspecting the metadata 994 associated with the read-only data snapshot2.

Once the data of block to be updated has been identified, the storageservice 990 can copy the data block to a storage location associatedwith the read-write storage layer for the storage volume 1 and thenupdate contents of the copied data block based on the data contained inthe data update request. In FIG. 9, the storage service 990 thisdepicted as transmitting a block update command 998.4 to the storagedevice 930 to copy the data block to be updated (for example data block970.B) to the storage location 984 associated with the read-writestorage layer of the storage volume 1 as data block 980.2, and then tomodify the contents of the data block 980.2 using the data received inthe data access request 944. In at least one embodiment, the blockupdate command 998.4 can comprise more than one data operation command.

The storage service 990 can then update the metadata 996 for the storagevolume 1 to associate a pointer to the updated data block 980.2 with theaddress of the data block received in the data access request 944. Ifthe storage service 990 receives a subsequent data access requesttargeting the data block, the storage service 990 can inspect themetadata 996 and determined that the target of the read operation is thedata block that was the target of previous update operation. The storageservice 990 can then process the data read request using the updateddata block 980.2 by following the pointer in the metadata 996 associatedwith the data block address.

The storage service 990 can determine that a data access requestcomprises a request for a data block associated with a read-only datasnapshot. The storage service 990 can process the request, at least inpart, by retrieving the data block from a storage device of thedistributed block storage devices 920-930. For example, storage service990 can determine that the data access request 946 is a read request fora data block. The storage service 990 can use the metadata (e.g., 992and/or 994) to identify a location where the requested data block isstored in the distributed block storage devices 920-930. In FIG. 9, thestorage service 990 this depicted as determining, using the metadata 992for the read-only data snapshot 1, that the data access request 946 is arequest for the data block 960.4. The storage service 990 transmits ablock read command 998.6 to the storage device 920 to retrieve the datablock 960.4 from the storage location 962 associated with the read-onlydata snapshot 1. The storage device 920 transmits a response 952comprising the data block 960.4 to the storage service 990.

The storage service 990 can determine that the data access request 948comprises a request for a data block. Using the snapshot metadata 994,the storage service can determine the request is for the data block970.B. The storage service 990 can then transmit a block read command998.8 to the storage device 930 to retrieve the data block 970.B fromthe storage location 970 associated with the read-only data snapshot 2.The storage device 930 transmits the response 954 comprising the datablock 970.B to the storage service 990.

In response to receiving a requested data block from one of thedistributed block storage devices 920-930, the storage service 990 cantransmit the received data block to the virtualization container 910.For example, after receiving the data blocks 960.4 and 970.B from thestorage devices 920 and 930, respectively, the storage service 990transmits a response 956 to the virtualization container 910 comprisingthe data blocks 960.4 and 970.B. Although the response 956 is depictedas comprising both the data blocks 960.4 and 970.B, the storage service990 can be configured to transmit received a blocks in separateresponses as well.

In at least one embodiment, the virtualization container 910 cantransmit a request to the storage service 990 to create a new snapshotbased on the storage volume 1. The storage service 990 can identify oneor more data blocks stored in the distributed block storage devices920-930 associated with a read-write storage layer of the storagevolume 1. For example, the storage service 990 can inspect the metadata996 to identify the storage locations in the distributed block storagedevices 920-930 associated with the read-write storage layer for thestorage volume 1 (e.g., 982 and 984). After identifying the one or moredata blocks associated with the storage volume 1 (e.g., 980.1 and980.2), the storage service 990 can create a read-only snapshot of theidentified data blocks and store the read-only snapshot in thedistributed block storage devices 920-920. In one embodiment, thestorage service 990 identifies one or more available storage locationsin the distributed block storage devices 920-920 and stores the datablocks in the read-only snapshot in the identified one or more storagelocations. In a different or further embodiment, the storage service 990converts the storage locations 982 and 984 associated with the storagevolume 1's read-write storage layer to a new read-only snapshot.Creating the read-only snapshot can further comprise creating newmetadata stored at the storage service 990 for the new snapshot.

The storage service 990 can identify one or more different read-onlysnapshots, on which the storage volume was based, and create a new imagesnapshot manifest for a new container image based on the createdread-only snapshot. For example, the storage service 990 can determinethat the storage volume 1 is based on the read-only data snapshot 2,which in turn is based on the read-only data snapshot 1. The storageservice 990 can then create the image snapshot manifest and indicate inthe manifest that the created read-only snapshot is based on theread-only data snapshot 2, which in turn is based on the read-only datasnapshot 1. In at least one embodiment, the storage service 990 can thentransmit the image snapshot manifest to image repository server.

Another virtualization container (not shown) can be configured totransmit a request to the storage service 990 to generate a new remotestorage volume based on the new container image. The anothervirtualization container can then, for example, present a virtualstorage volume that is associated with the new remote storage volume toa process running in the another virtualization container as if it was aphysical storage volume connected to the another virtualizationcontainer. The storage service 990 can be configured to receive such arequest and to generate the new remote storage volume based on the newcontainer image. For example, the storage service 990 can analyze theimage manifest to identify the multiple read-only data snapshotsassociated with the new container image and to create a new remotestorage volume associated with the identified read-only snapshots. In atleast one embodiment, creating the new remote storage volume comprisescreating new storage volume metadata on the storage service 990 thatassociates the new storage volume with the identified read-onlysnapshots stored in the distributed block storage devices 920-930.

FIG. 10 is a system diagram showing an example system 1000 configured topresent a mounted volume 1014 to an application 1012 in a virtualizationcontainer 1010 based on a layered virtual volume 1032 in the distributedstorage 1030. A storage driver 1016 is configured to present arepresentation of the mounted volume 1014 to the application 1012 basedon data stored in the layered virtual volume 1032. The storage driver1016 is configured to treat read-only snapshots 1042-1044 as if theywere read-only image layers 1024-1026. However, instead of copyingread-only snapshots 1042-1044 locally to a storage device connecteddirectly to a host computer containing the virtualization container1010, the storage driver 1016 accesses the read-only snapshots 1042-1044in the distributed storage 1030 over a network. The storage driver 1016is configured to treat the read-write virtual volume 1032 as if it werea read-write container layer 1022 stored locally. When the storagedriver 1016 receives a request to add, modify, and/or delete data in themounted volume 1014 from the application 1012, the storage driverprocesses the request using the read-write virtual volume 1032 and oneor more of the read-only snapshots 1042-1044 stored in the distributedstorage 1030.

In at least one embodiment, the distributed storage 1030 comprises acaching layer (not shown) where frequently accessed data stored in thedistributed storage 1030 can be accessed more quickly than if the datawas retrieved from storage locations in the distributed storage 1030.The storage driver 1016 can be configured to access frequently usedsnapshot and virtual volume data in such a caching layer in order toimprove data access times.

In a different or further embodiment, the storage driver 1016 can storemetadata describing data locations of data in the virtual volume 1032and/or the read-only snapshots 1042-1044. The storage driver 1016 canuse such metadata to identify one or more locations of data requested bythe application 1012 before transmitting any data requests to thedistributed storage 1030.

In a different or further embodiment, data associated with the virtualvolume 1032 and/or the read-only snapshots 1042-1044 can be storedredundantly across multiple storage devices in the distributed storage1030. In such an embodiment, the storage driver 1016 can be configuredto process data access requests received from the application 1012 bytransmitting requests for data to multiple storage devices in thedistributed storage 1030.

FIG. 11 depicts a generalized example of a suitable computingenvironment 1100 in which the described innovations may be implemented.The computing environment 1100 is not intended to suggest any limitationas to scope of use or functionality, as the innovations may beimplemented in diverse general-purpose or special-purpose computingsystems. For example, the computing environment 1100 can be any of avariety of computing devices (e.g., desktop computer, laptop computer,server computer, tablet computer, etc.).

With reference to FIG. 11, the computing environment 1100 includes oneor more processing units 1110, 1115 and memory 1120, 1125. In FIG. 11,this basic configuration 1130 is included within a dashed line. Theprocessing units 1110, 1115 execute computer-executable instructions. Aprocessing unit can be a general-purpose central processing unit (CPU),processor in an application-specific integrated circuit (ASIC) or anyother type of processor. In a multi-processing system, multipleprocessing units execute computer-executable instructions to increaseprocessing power. For example, FIG. 11 shows a central processing unit1110 as well as a graphics processing unit or co-processing unit 1115.The tangible memory 1120, 1125 may be volatile memory (e.g., registers,cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory,etc.), or some combination of the two, accessible by the processingunit(s). The memory 1120, 1125 stores software 1180 implementing one ormore innovations described herein, in the form of computer-executableinstructions suitable for execution by the processing unit(s).

In at least some embodiments, the computing environment 1100 can be usedas an example host computer as described herein. In different or furtherembodiments, the computing environment 1100 can be used as a servercomputer comprising a storage service as described herein.

A computing system may have additional features. For example, thecomputing environment 1100 includes storage 1140, one or more inputdevices 1150, one or more output devices 1160, and one or morecommunication connections 1170. An interconnection mechanism (not shown)such as a bus, controller, or network interconnects the components ofthe computing environment 1100. Typically, operating system software(not shown) provides an operating environment for other softwareexecuting in the computing environment 1100, and coordinates activitiesof the components of the computing environment 1100.

The tangible storage 1140 may be removable or non-removable, andincludes magnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, orany other medium which can be used to store information in anon-transitory way and which can be accessed within the computingenvironment 1100. The storage 1140 stores instructions for the software1180 implementing one or more innovations described herein. In at leastsome embodiments, storage 1140 comprises one or more of the examplestorage devices as described herein.

The input device(s) 1150 may be a touch input device such as a keyboard,mouse, pen, or trackball, a voice input device, a scanning device, oranother device that provides input to the computing environment 1100.The output device(s) 1160 may be a display, printer, speaker, CD-writer,or another device that provides output from the computing environment1100.

The communication connection(s) 1170 enable communication over acommunication medium to another computing entity. The communicationmedium conveys information such as computer-executable instructions,audio or video input or output, or other data in a modulated datasignal. A modulated data signal is a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia can use an electrical, optical, RF, or other carrier.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthbelow. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed methods can be used in conjunction with other methods.

Any of the disclosed methods can be implemented as computer-executableinstructions stored on one or more computer-readable storage media(e.g., one or more optical media discs, volatile memory components (suchas DRAM or SRAM), or non-volatile memory components (such as flashmemory or hard drives)) and executed on a computer (e.g., anycommercially available computer, including smart phones or other mobiledevices that include computing hardware). The term computer-readablestorage media does not include communication connections, such assignals and carrier waves. Any of the computer-executable instructionsfor implementing the disclosed techniques as well as any data createdand used during implementation of the disclosed embodiments can bestored on one or more computer-readable storage media. Thecomputer-executable instructions can be part of, for example, adedicated software application or a software application that isaccessed or downloaded via a web browser or other software application(such as a remote computing application). Such software can be executed,for example, on a single local computer (e.g., any suitable commerciallyavailable computer) or in a network environment (e.g., via the Internet,a wide-area network, a local-area network, a client-server network (suchas a cloud computing network), a data center, or other such network)using one or more network computers. A computer-readable storage mediumcan be a storage device, as described herein.

For clarity, only certain selected aspects of the software-basedimplementations are described. Other details that are well known in theart are omitted. For example, it should be understood that the disclosedtechnology is not limited to any specific computer language or program.For instance, the disclosed technology can be implemented by softwarewritten in C++, Java, Perl, JavaScript, assembly language, or any othersuitable programming language. Likewise, the disclosed technology is notlimited to any particular computer or type of hardware. Certain detailsof suitable computers and hardware are well known and need not be setforth in detail in this disclosure.

It should also be well understood that any functionality describedherein can be performed, at least in part, by one or more hardware logiccomponents, instead of software. For example, and without limitation,illustrative types of hardware logic components that can be used includeField-programmable Gate Arrays (FPGAs), Program-specific IntegratedCircuits (ASICs), Program-specific Standard Products (ASSPs),System-on-a-chip systems (SOCs), Complex Programmable Logic Devices(CPLDs), microprocessors, etc.

Furthermore, any of the software-based embodiments (comprising, forexample, computer-executable instructions for causing a computer toperform any of the disclosed methods) can be uploaded, downloaded, orremotely accessed through a suitable communication means. Such suitablecommunication means include, for example, the Internet, the World WideWeb, an intranet, software applications, cable (including fiber opticcable), magnetic communications, electromagnetic communications(including RF, microwave, and infrared communications), electroniccommunications, or other such communication means. *The disclosedmethods, apparatus, and systems should not be construed as limiting inany way. Instead, the present disclosure is directed toward all noveland nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and subcombinations withone another. The disclosed methods, apparatus, and systems are notlimited to any specific aspect or feature or combination thereof, nor dothe disclosed embodiments require that any one or more specificadvantages be present or problems be solved.

In view of the many possible embodiments to which the principles of thedisclosed invention may be applied, it should be recognized that theillustrated embodiments are only preferred examples of the invention andshould not be taken as limiting the scope of the invention. Rather, thescope of the invention is defined by the following claims. We thereforeclaim as our invention all that comes within the scope of these claims.

What is claimed is:
 1. A system comprising: a host computer and avirtualization container instantiated on the host computer, wherein thevirtualization container is configured to: present a virtual storagevolume to a process executing in the virtualization container as aphysical storage volume connected to the virtualization container, andtransmit a data access request for the virtual storage volume to astorage service, separate from the host computer, to access data storedon a remote storage volume; the storage service, configured to: receivethe data access request, access the remote storage volume on a storagedevice, wherein the remote storage volume is associated with one or moreread-only data snapshots, and process the data access request using atleast one of the one or more read-only data snapshots; anothervirtualization container instantiated on another host computer, whereinthe another virtualization container is configured to: execute anotherprocess in isolation from one or more other processes executing on theanother host computer, present a different virtual storage volume to theanother process as a different physical storage volume connected to theanother virtualization container, and transmit data access requests forthe different virtual storage volume to the storage service to accessdata stored in another remote storage volume; and wherein the storageservice is further configured to: receive the data access requests fromthe another virtualization container, and access the another remotestorage volume on the storage device over the network, wherein theanother remote storage volume comprises at least one of the one or moreread-only data snapshots associated with the remote storage volume. 2.The system of claim 1, wherein the data access request is a request toperform a data write operation; and the storage service is furtherconfigured to: identify a data block in one of the one or more read-onlydata snapshots that is a target of the data write operation, copy theidentified data block to a read-write storage space in the storagedevice, the read-write storage space being associated with the remotestorage volume, and modify the copied data block in the read-writestorage space according to the data write operation.
 3. The system ofclaim 2, wherein the storage service is further configured to: receive asubsequent data access request to perform a data read operationtargeting the data block; determine that the target of the data readoperation is the data block that was the target of the previous datawrite operation; and transmit the modified data block in the read-writestorage space to the virtualization container.
 4. The system of claim 2,further comprising: a second storage device storing the read-writestorage space associated with the remote storage volume.
 5. The systemof claim 2, wherein: the virtualization container is further configuredto: transmit a request to the storage service to create a new containerimage based on the remote storage volume; and the storage service isfurther configured to: receive the request to create a new containerimage; and create a new read-only data snapshot comprising the modifieddata block in the read-write storage space.
 6. The system of claim 5,wherein the storage service is further configured to: generate an imagemanifest for the new container image describing the container image ascomprising the new read-only data snapshot and the one or more read-onlydata snapshots associated with the remote storage volume.
 7. The systemof claim 6, further comprising an image repository configured to:receive the image manifest from the storage service; and associate itwith an identifier for the new container image.
 8. The system of claim5, further comprising: a second host computer and a secondvirtualization container instantiated on the second host computer,wherein the second virtualization container is configured to: execute asecond process in isolation from one or more other processes executingon the second host computer, transmit a request to the storage serviceto generate a new remote storage volume based on the new containerimage, and present a second virtual storage volume, associated with thenew remote storage volume, to the second process as a physical storagevolume connected to the second virtualization container; and wherein thestorage service is further configured to: receive the request togenerate the new remote storage volume based on the new container image,determine that the new read-only data snapshot is associated with thenew container image, and create a new remote storage volume associatedwith the new read-only data snapshot.
 9. The system of claim 1, whereinthe accessing the remote storage volume on the storage device comprisesaccessing a distributed storage.
 10. A method comprising: presenting avirtual storage volume to a process as a physical storage volume,wherein the process is executing in a virtualization container;receiving a request for data in the virtual storage volume at a storageservice separate from the virtualization container, wherein the dataaccess request comprises a request to perform a data write operation;accessing a remote storage volume on a storage device, wherein theremote storage volume is associated with one or more read-only datasnapshots; and processing the request for data using the one or moreread-only data snapshots, comprising: identifying a data block in one ofthe one or more read-only data snapshots that is a target of the datawrite operation, copying the identified data block to a read-writestorage space in the storage device, the read-write storage space beingassociated with the remote storage volume, and modifying the copied datablock in the read-write storage space according to the data writeoperation.
 11. The method of claim 10, further comprising: receiving asubsequent data access request to perform a data read operationtargeting the data block; determine that the target of the data readoperation is the data block that was the target of the previous datawrite operation; and transmit the modified data block in the read-writestorage space to the virtualization container.
 12. The method of claim10, further comprising: storing the read-write storage space in astorage device associated with the remote storage volume.
 13. The methodof claim 10, further comprising: receiving a request to create a newcontainer image based on the remote storage volume; and creating a newread-only data snapshot comprising the modified data block in theread-write storage space.
 14. The method of claim 13, furthercomprising: generating an image manifest for the new container imagedescribing the container image as comprising the new read-only datasnapshot and the one or more read-only data snapshots associated withthe remote storage volume.
 15. The method of claim 14, furthercomprising: receiving the image manifest from the storage service; andassociating it with an identifier for the new container image.
 16. Themethod of claim 10, wherein accessing the remote storage volume on thestorage device comprises accessing a distributed storage service.
 17. Asystem comprising: a virtualization container comprising a storagedriver, wherein the storage driver is configured to: present a virtualstorage volume to a process executing in the virtualization container asa physical storage volume connected to the virtualization container, andtransmit a data access request for the virtual storage volume to astorage service, wherein the data access request is a request to performa data write operation; and the storage service, wherein the storageservice is configured to: receive the data access request, access theremote storage volume on a storage device, wherein the remote storagevolume is associated with one or more read-only data snapshots, andprocess the data access request using at least one of the one or moreread-only data snapshots, comprising: identify a data block in one ofthe one or more read-only data snapshots that is a target of the datawrite operation, copy the identified data block to a read-write storagespace in the storage device, the read-write storage space beingassociated with the remote storage volume, and modify the copied datablock in the read-write storage space according to the data writeoperation.
 18. The system of claim 17, wherein: accessing the remotestorage volume on the storage device comprises accessing a distributedstorage.